Matplotlib is a python library for making publication quality plots using a syntax familiar to MATLAB users. Matplotlib uses numpy for numerics. Output formats include PDF, Postscript, SVG, and PNG, as well as screen display.

Tool Command Language (Tcl) is an interpreted language and very portable interpreter for that language. Tcl is embeddable and extensible, and has been widely used since its creation in 1988 by John Ousterhout.
Bug reports to http://core.tcl.tk/tcl/
Follow code development at http://core.tcl.tk/tcl/

KDiff3 is a graphical text difference analyzer for up to 3 input files, provides character-by-character analysis and a text merge tool with integrated editor. It can also compare and merge directories. Platform-independant.

Free editor for PDF documents. Complete editing of PDF documents is possible with PDFedit. You can change raw pdf objects (for advanced users) or use many gui functions. Functionality can be easily extended using a scripting language (ECMAScript).